Several frequency source identification methods are generally known in the prior art. The most well known of these is probably what may be termed "standard heterodyning techniques". This technique tunes a heterodyne receiver for peak output provides a readout of the frequency in question. This technique is relatively time consuming and becomes impossible when the signal source is hopping or changing rapidly in frequency. One known technique for signal detection where signal hopping is involved involves the use of a compressive receiver. In this type of receiver, an input signal is mixed with a chirp signal and swept through the intermediate frequency band for a designated time of arrival. The signal's position and time is therefore indicative of its frequency. One example of this type of apparatus is disclosed in U.S. Pat. No. 4,443,801 issued to D. R. Klose et al, which issued on Apr. 17, 1984, and which discloses the use of SAW interferometer processor apparatus which performs high resolution measurements on multiple signals of different frequency.
A SAW channelizer compressive interferometer is a combination of two basic and well known technologies, namely, a SAW channelizer and a compressive interferometer. A conventional SAW channelizer measures the pulsewidth (PW), pulse amplitude (PA), and time of arrival (TOA) while compressive angles of arrival (AOA) channels measure AOA and frequency. A SAW channelizer is comprised of a contiguous bank of SAW filters arranged to sort the received signal into frequency bins, with the frequency bin width being selected by the minimum pulsewidths to be intercepted. The filters also have sharp cut off frequencies to enable them to discern strong vs. weak signals in adjacent channels. A compressive interferometer is a spin off of a microscan receiver where AOA is measured from antenna input phase differentials along with the frequency of multiple signals in the IF passband. Conventional SAW based compressive interferometers, however, suffer from having too many filters in the channelizer to measure pulsewidth.